In optical systems for transmitting signal intelligence by light energy, it is most important in employing single filament fiber optic cable that the ends of such fiber optic cable be joined in precise alignment to assure minimum light losses in the transmittance of light energy from one cable end to another.
State of the art single filament fiber optic cable may typically have an outside diameter of five thousandths of an inch, including the cladding, and a core diameter of the fiber of three thousandths of an inch. In order to avoid undue, undesirable, excessive light losses in a connector which joins two such cable ends, the alignment limits should be of the order of plus or minus two microns. Additionally, of course, as logically follows, the gap between the ends of the fibers must be extremely small for good transmittance between the fiber optic cable ends. By far, however, the major difficulty and problem is posed by the requirement of alignment of two such very small diameter fiber optic cable ends within the extremely stringent limits of plus or minus two microns.
In the prior art, because it was not possible to conveniently and readily drill holes in a metal terminal end material having the extremely small internal diameter of the order of five thousandths of an inch, other alternative approaches have been contrived. One of these approaches required that the four corners on four small pieces of a suitable metal, such as brass, be angularly milled at 45.degree. to remove approximately three thousandths of an inch of the corner material. The four brass pieces were then assembled in a square, with each of the milled corners on the inside, forming a rectangular or square elongate cavity to receive and contain the end of the fiber optic cable. The four pieces of material so assembled were then soldered or bonded in an appropriate manner at their interfaces. However, it was found almost impossible to bond or solder the interfaces between the four elements without some solder or bonding material creeping into the cavity.
A second alternative method was devised which eliminated two of the interfaces. This latter method required that a high precision, extremely small groove be milled in each of two matching pieces of suitable material such as brass, for instance. When joined, the two pieces formed a square elongate cavity for receiving and supporting a single filament fiber optic cable end. The two pieces were affixed to each other by bonding or soldering, for example; but joining the two pieces to form a unitary terminal element for a single filament fiber optic cable was found to be difficult because of the creep of solder or bonding material into the square elongate cavity.
A further expedient was attempted by filling the square elongate cavity with a material that solder would not wet, nor adhere to bonding material. After the terminal member had been soldered or bonded into a unitary assembly, the filling material within the cavity was removed. However, considerable difficulty was experienced in efficiently removing the fill material from the elongate square cavity and, moreover, in many cases it was found to be difficult to insert the end of a single filament fiber optic cable into the cavity.
Accordingly, the need exists for a new type of connector which will align extremely small diameter single filament fiber optic cables to assure minimal light losses at the point of such connection, since drilling holes in a metallic or similar type of material having an internal diameter of the order of five thousandths of an inch is not readily accomplished; furthermore even when such holes are successfully drilled in a suitable terminal material, the desired alignment cannot be assured because of the tendency of such extremely small drills to bend and flex during the drilling operation.
Therefore, it is highly desirable that a new and improved single filament fiber optic cable connector be provided which can be fabricated by comparatively conventional methods and function to transmit light from one such single filament fiber optic cable end to another with minimal light loss as is assured by end-to-end alignment along a single axis within plus or minus two microns.